Hippocamp

Sometimes it's not wise to go swimming, if it's known that the area is inhabited by a herd of hippocamps. The hippocamps, also called sea horses and water horses, are horse-like creatures with the lower body of a fish, sometimes of a dolphin. Some individuals also might have fin-like wings on their back or tail.
Even though the hippocamps are usually timid and wary of strangers and people in general, they can get furious if their herd is threatened, especially if someone wants something bad for their foals. They are also rather wise and sadly, they also taste good. Some people say that the various bodyparts of a hippocamp are magical and some parts of the creature, like mane or fur, is often used in alchemical concoctions.